If you're building iOS apps, you have no excuse to not test betas frequently.
iOS8 integrates with TestFlight, so even nontechnical users can easily try your beta apps. It takes seconds to send out beta releases to testers and there is no manual review process. "Normal" app release cycles are once-per-month, but that's incredibly slow for beta testing. I send a new beta release every 2 days and get immediate feedback.
Alternately I would suggest user testing to #11. In the event you can't do some kind of private release to get early user feedback, or you want unbiased usability testing from people outside your company. Bring people in to play with your app, guide them through some tasks and see how they use it and what they think certain parts of the app do.
You don't even need to have a functioning build for this to work. Prototypes work too
iOS8 integrates with TestFlight, so even nontechnical users can easily try your beta apps. It takes seconds to send out beta releases to testers and there is no manual review process. "Normal" app release cycles are once-per-month, but that's incredibly slow for beta testing. I send a new beta release every 2 days and get immediate feedback.